A typical gas discharge light fixture includes a ballast and a gas discharge lamp. The ballast converts standard line voltage and frequency to a voltage and frequency suitable for the specific type of lamp. The gas discharge lamp converts electrical energy into visible light with high efficiency. Various forms of gas discharge light fixtures exist, for example, a single ballast may be coupled to several lamps or several ballasts may be coupled to several lamps.
Conventional gas discharge lamps are generally straight elongated tubes of essentially circular cross section with varying outside diameters ranging between about five-eighths and one and one-half inches. Compact gas discharge lamps differ from conventional gas discharge lamps in that they are constructed of smaller diameter tubing, typically having an outside diameter of less than about five-eighths of an inch. Also, the lamps are compact in part because the tubing has one or more small radius bends that allow the tube to fold back on itself in such a manner as to achieve a compact shape. Additionally, in compact gas discharge lamps wherein the tube is folded back on itself, the lamp ends typically are in close proximity to each other.
Compact gas discharge lamps and ballasts are generally designed to operate within specified temperatures. The specified temperatures are dependent upon the output level of the light being provided by the lamp. For example, a compact gas discharge lamp operating at its full rated light output level, referred to as its nominal light output level, is designed to operate at greater temperatures than a compact gas discharge lamp operating at 1% of its nominal light output level. If the gas discharge lamp is operated at a low output light level at too high a temperature, the light tends to flicker.
This phenomenon is particularly noticeable when dimming a compact gas discharge lamp from its nominal light output level to a low light output level, such as 1% of its nominal level. The flicker can be annoying. Further, the flicker could be interpreted as a malfunction in the lamp, the ballast, or other associated component of the lighting system.
Accordingly, there is a need for a lighting system capable of providing stable, flicker-free light when dimming a compact gas discharge lamp to below about one percent of the lamp's nominal light output level.